Telephone system



Sept. 9, 1930. 1R. F. GOULD 1,775,522

TELEPHONE SYSTEII Filed. Dec. 1, 1927 3 Sheets-Sheet 1 Ra EEuuld.

Sgpt. 9, 1930. R. F. GOULD mmamorm syswu Filed Dec. 1. 1927 3 Sheets-Sheet 2 N MNN QNN -N Sept. 9,.1930. R. F. GOULD I 1,775,522

TELEPHONE SYSTEI Filed Dec. 1, 1927 3 Sheets-Sheet 3 nor rinno Patented Sept. 9, 1930 UNITED mm on KANSAS ci'im'ivr ssouni, A CORPORATION or DELAWARE TELEPHONE SYSTEM. 1

Application filed. December 1,- 1927. Serial No. 236,937.

i The presentinvention relatesto, telephone syste1ns,and hasto do more particularly with provisions in a private branch exchange, for ,B'St-itbllShlIlg connections between the sub scriber therein, as well as with equipment for taking careoigthe traffic between a private branch exchange and a inainexchange. I e The principal objectiof the invention resides in the provision of improved circuit arrangernents and equipment embodying desirable features and advantages in an .eiiicient,

simple aiideconomic manner.

One feature has to do with the provison .oialine finder switch associated with a connector SWltGh, for lIltGIOOllIleCtlIlg a calling line w th a called line, and means, includ ng finder distributor switch common to .a plurality of'line finders, for preventing the actuation of more than one finderswitch in respouse to the initiationof a call at a substation in a private branch exchange.

Another feature of the invention resides in means associated with subscribers lines in a 1 private branch exchange and cooperating with means in connectors. and finder switches for permitting certain subscribers to extend attendant in the extension of calls,and provision of such apparatus within the attendants cabinet in order to render'an efli- -cient and simple unit. 7

A further feature resides invarious relays an dotli'er apparatus individual to a trunk from a mainexchange .to a private exchange,

and in combining such equipment "with a j connector switch accessible to the trunk.

1 Other featuresrelate to novel provisions and methods for transmitting impulses from vate branch exchange. and toswitches in the main exchange in ordentoext'end calls,= and to novel provisions and methods for ytransmain exchange and terminating in" an at- "PATENT OFFICE GOULD,-- or ciiic ieo, IL'LInoIs, ASSIGNOR 'ro RESERVE HOLDING COMPANY,

mitting ringing current to called stations in the private branch exchange.

The novel features through the provision} of which the above mentioned and other de- 'sirable results are obtained will be described sheetsof drawings, in whichin connection with the accompanying three 'ina private branch exchange, as well as a finder switch and connector switch for establishing a connection between the stations,and the p'rovisionof a finderldistributor switch ,for controlling the actuation ofthe finder switches; r y M i i J Fig. 2 shows a trunk line extending from a Eigql illustratessubscribers? substations tendants cabinet in a private branch ex change. This figure also shows various keys tendant cabinet, ands groupofrelayspwhich ay be QQ Gred commonto a plurality of trunk lines;and I v cabinet. Various relays, andother] apparatus, which are individual to a trunk line have *been, combined with the connector shown in this figure.

and: other equipment associated with the at- Referring now particularly to Fig. 1, at

the left there is illustrated a calling substabridged across. the line conductors? and The line conductors terminateat the ex- '1 change in. a line equipment comprising the relays 10 and 15.

ition inpthe private branch exchange, This v The line finder ,F associated with a connector C, and its actuation is controlled by a finder distributor switch FD shown inn the,

H v lOWEIijEZLI't ofthe drawing. The connector an attendants cabinetto switches in thepricomprises a number of 'relays and, other lie the right of the drawings, and it has also access to the attendants cabinet and to the trunk line extending to the main exchange.

Having described in general the apparatus illustrated in Fig. 1, the operation of this equipment in establishing a connection be tween the calling subscriber A and the called subscriber B shall now be described in detail.

Each line terminates in a line and cut oil relay 10 and 15, respectively, which cause the preselected finder, such as F, to find the line when the receiver is removed at the substation in order to extend a call. Vhen the line is found, the finder extends the line through to the associated connector switch G and the distributor switch FD is caused to operate and to preselect another free finder switch.

When the receiver at the substationA is removed, relay 10 is energized over its upper winding in series with the calling line, its circuit extending from battery, upper winding of relay 10, armature 16 and its resting contact, line conductor 7, loop of the substation A, line conductor 8, resting contact and armature 18, to ground. Relay 10 operates and removes at its armature 11 ground from a contact in the finder switch bank accessible to wiper 23 of the finder switch, in order to permit the preselected finder to find the calling line. At its armature 12, the relay 1O closes a circuit for the relay 41 of the finder distributor, from ground, resting contact and armature 17, make contact and armature 12, resting contact and armature 37, and winding of relay 41 to battery.

Assuming that the wipers of finder switch F which was preselected by the finder distributor FD in a manner which shall be described subsequently, are in engagement with the contacts of the calling lineA, relay 41 of the finder distributor, upon operating, causes the connector switch C associated with the finder F to connect its line relay 57 across the calling line. This operation will be described presently. It shall be assumed first that the finder is not resting in engagement with the calling line, and, accordingly the operation of the finder switch F in connection with seeking the calling line will be described next.

Upon operating, the relay 41 in the finder distributor FD closes a circuit for the motor magnet of the finder, from battery, wind ing of the motor magnet 25, interrupter con-- tact 26, contact in the bank of the distributor accessible to wiper 32, armature 42 and its make contact, wiper 33, resting contact and armature 54, wiper 23. of the finder switch, armature 11 and its resting contact to ground. In order to understand this circuit, it must be remembered that the finder in question is not in engagement with the calling line, but with a line which is assumed to be in the condition of rest as shown in the drawing, that is, with its line relay 10 in normal position. Accordingly, the wiper 23 of the finder switch which is supposed to hunt for the calling line encounters ground over the armature 11 of the line relay 10. Relay 41, upon operating, also attracts its armature 43 and connects thereby ground tothe winding of relay 39. This relay, however, is prevented from operating at this moment on account of being short circuited to ground over wiper 23 of the finder switch and armature 42 of relay 41. As long as the finder switch F is seeking the calling line, its wiper 23 will encounter ground, and relay 39 in the finder. distributor switch will be prevented from energizing. The motor magnet 25 of the finder switch operates, interrupting its own circuit at interrupter contact 26, restores, and advances the wipers 21 to 24, inclusive, over the associated bank contacts. The foregoing operation continues until the calling line is found.

When the calling line is found,wiper 23 will not encounter ground since armature 11 of line relay 10 is in operated position, and the motor magnet 25 will cease to operate. The short circuit around the winding of relay 39 is removed at the present moment, and this relay energizes in series with the motor magnet of the finder switch from ground at armature 43. The motor magnet 25 does not operate in series with relay 39 on account of the high resistance of this relay. Relay 39 operates its armature 40, thereby closing a circuit for energizing relay 36. At its armature relay 39 closes a circuit for the lower winding of relay of the connector switch C. The latter circuit, it will be seen, extends over wiper 31 of the distributor. The function of relay 36 of the distributor will be explained presently. However, it should be noted at this time that relay 36 opens at its armature 37 the circuit for the slow acting relay 41, in order to prevent other calls from being extended through to a connector until the distributor has selected another finder.

Relay 50, upon operating, attracts its arma ture 55, and removes thereby ground from a contact in the distributor bank accessible to wiper 34. Every connector keeps a multiple ground connected to this contact, accessible to wiper 34, by means of armatures of the various relays 50. The purpose of this multiple ground is to stop a distributor in case all finders should be found busy. The overflow register 45 will be operated in such a case in order to indicate the condition. Detailed description of this operationwill be presented later on.

At its armature 54 the relay 50 opens the connection of the wiper 23 of the finder switch with a bank contact of the distributor switch and connects ground to the wiper 23 in order to energize the cut-off relay 15 in series with the lower winding of the line relay 10, by way of armature 11 of the line re My 10. --This ground also extends to the is oi'z importance in connection with discriminating service in which a' certain subscriber is'prevente from calling out into the main exchange. The connector C has access to trunk'lines-terminating in the main exchange, overa certain level, and when the connector is operatedtothis level thecontact springs 110, lll and 112 will be operated, and the wiper 22 of the finder switch will be extended by way ofthe armature 52 to the private wiper 1030f the connector switch. If a line,

which .is not permitted to call to the main exchange, attempts such a-call, ground will be extended over the discriminating conductor 13 and the/wiper 22 of the finder switch K to the private wiper 103, which produces conditions with respect to the circuits of-the connector, present only in caseallthe trunk lines accessible to the connector in that level should he busy. Accordingly, the connector will roi tate automatically and the subscriber who is not entitled to call to the mainexchange will receive a busy signal. This'operation will be described presently in detail.

At armatures 51 and 56, the relay 50 extends thel ine circuit of thecalling station. to the line relay 57 of the connector switch.

Relay 15 of the line circuitwas operated over a circuit including the armature 54 relay 50. At armature 16 this relay opens the circuit over the upper winding of line relay atarmature 17 ground is removed from the circuit over which relay-41was originally energized; and at armature 18 ground 1s removed from the line conductor 8. Linerelay 10 remains energized. in series with thecut oft relay to ground over the attracted ar-V mature54 of relay 50. The calling line is thus cleared of attachments and, connected through to the line relay '57 of the connector, which circuit can be traced from battery, upper winding of relay 57,resting contact and armature 7 8, armature 51 and its make contact, wiper 21 of the finder switch line conductor 7 loop of the calling substation A, line conductor 8, wiper 24 of-the finder switch, make contactand armature 56, armature 81 and its restingcontac't, lower winding of the line relay 57 contact spring 116 of the 011- normal contacts and conductor 116', which terminates in a tone source for conveying to the calling,subscriber ithat he may operate his calling'device inorder to transmit 1mpulses tothe connector.

Line relay 57 operates its armature 58, completing therebya circuit for the slow acthas access should. initiate a can;

ing release relay: 59'.v The ,latter relay actuates armature 6O connecting ground tohthe holding conductor 6O to which is connected the holding windingofrelay 50 over the armature 53. t This prevents the relay from deenergizing when. its original circuitincluch ing its lower winding is opened by the finder distributor preselecting another finder switch;

At armature 61, the relay 59 opens a point in i the circuit or therelease magnet. 108 and 1 closes a point in the impulsing circuit; and at armature 62gr'ound is connected toa con tact in the bank of the .finder distributor in' order to markthe associated finder busy; l

i The operationsot the finder distributor in k preselecting an idle finder switch will be described neXt. i i

It will be rememberedthat relay39was energized to close a circuit for relay 36 at its armature 40. Relay 36operates. its armaflture 38 and connects thereby the circuit of the motor magnet of the .distributorswitch from battery, winding of the motor magnet 35, make contact and armature 44, armature 38 and its make contact, make contact and; armature .40 to ground. At armature 37jthe relay 36 interrupts the circuit, of the slow acting relay 41. Thiswrelay, however, does not fallback immediately on account of being slow acting,=and, therefore, the circuit for the motor magnet is initially established over. attracted armature 44. WVhenrelay 41 deenergizes it opens the circuit of the motor 1 magnet 35, which deenergizes and advances the wipers 31 to 34, inclusive,byone step.

The relay 41also opens thecircuit of .re-

1 y'39 at its armature 43. In case the wipers are now' in engagement with an idle finder switch, relay 39, upon deenergizing, removes ground from thedistributor wiper31, and opens at its armature. thecircuitofmotor magnet 35 and of relay 36. Therefore, the

wipers of the distributor come to rest and .an idle finder switch is thus preselected and prepared to be actuated to hunt fora line in 7110 case a subscriber to which the finder switch 1 Assuming, however thatthe distributor switch has advanced its wiper intov engagement with a busyfinder switch, the wiper 34 i will encounter ground over anarmature 62 of 3 an operated relay 59 of a connector. which. is

associated with that busy. finder switch, and a circuit will be closed for maintainingythe relay 36 of the distributor in operated posi-"r ,tion. The ground encountered by wiper 34 of the distributor is also transmitted byway of armature38 to the motor magnet 35, which operates again, opening, "its interrupter springs 35 and therebyinterrupting itsown circult for advancingits wipers into engagement withlanotherset of bank. contacts associated with another finder switch. This opa i eration continues until the wiper 34 finds an idle finder switch, that is, acon'tactwhich is not grounded by an armature such as 62 of a relay 59.

In case all finder switches accessible to the distributor FD are busy, the wiper 34 will encounter ground over the winding 45 of an overflow register connected to the last bank contact. This bank contact is also connected in multiple to armatures such as 55 of relays 50, which, as long as a connector is idle, keep ground connected to this bank contact. When the last connector and with it the associated finder switch, is taken into use, the corresponding relay 50 removes ground at its armature 55 from the multiple contact. Therefore, when the wiper 34 reaches this bank contact, a circuit will be closed from ground, winding of the overflow register 45, bank contact accessible to wiper 34, winding of relay 36, to battery. Relay 36 does not energize in series with the windings of the overflow register 45 while the register operates to indicate the condition all finders busy. Relay 36, being prevented from energizing, releases its armature 38,0pening thereby the circuit of the motor magnet 35. The automatic rotation of the finder distributor is now prevented and the distributor stops until a finder becomes idle, that is, until an armature such as 55 connects a multiple ground to the contact with which the wiper 34 is in engagement. hen this occurs, relay 36 again operates, closing its armature 38 and causing the finder distributor to hunt for the idle finder switch. The overflow register 45, being short circuited by ground at armature 55 of relay 50, associated with the connector which has become idle, releases, while the finder distributor rotates its wipers to seek the idle finder. Relay 36 will remain energized and thus keep the circuit of the motor magnet 35 closed as long as wiper 34 encounters contacts associated with busy connectors, which contacts are grounded at armatures such as 62. However, when an idle finder is found, the wiper 34 will not encounter ground since the idle finder is one which is associated with an idle connector, in which the relay 59 is in deenergized position and keeps the armature 62 open, and relay 36 will, accordingly, deenergize and open the circuit of the motor magnet 35. Thus, the finder distributor comes to rest when an idle finder switch is found which can be used for extending another call.

It shall be assumed next that the subscriber at the calling station replaces his receiver at stage of the extension. When occurs, the circuit for the line relay 57 in the connector is opened. The line relay restores and opens the circuits to relay 59. Upon deenergizing, relay 59 removes ground from the bank contact accessible to wiper 34 of the distributor switch to make the associated finder switch free and opens the circuit of the locking winding of relay 50. Relay 5O restores and disconnects the connector from the line; removes ground from wiper 23 of the finder switch, thereby releasing the cut-off relay 15 and the line relay 10 and also removing the ground from the private normal conductor 9; places a multiple ground on the contacts accessible to wiper 34 of the distributor switch; and opens its armature 52, thereby interrupting the prepared circuit for discriminating service. Line relay 10 grounds the corresponding contact in a finder switch bank accessible to wiper 23 so that a finder seeking another calling line will not stop on these bank contacts.

The description of the operation of the connector switch in extending calls to the wanted station B will now be continued.

It will be remembered that the line relay 57 was energized over the loop of the calling station A and that the subscriber received a dial tone over the conductor 116 which indicated to him that he may operate his calling device in accordance with the digits of the desired subscribers number.

hen the subscriber operates his calling device, the line relay 57 will be interrupted a number of times in quick succession in ac cordance with the digit from which the dial was operated. At its armature 58, the line relay closes, at each interruption, a circuit for the slow series relay 63 and the vertical magnet 67. This circuit may be traced from ground, armature 58 and its resting contact, armature 61 an d. its make contact off normal springs 118, winding of relay 63, winding of the vertical magnet 67, battery. The wipers 102, 103, and 104 of the connector are raised by one step, and the various off-normal contacts are thrown into their alternate positions. The circuit for the lower winding of the line relay, which originally extends over springs 116 of the ofi normal contact, is opened, and a new circuit is closed including the ofi normal contacts 117. This disconnects the dial tone conductor 116'. Springs 118 over which the rotary magnet 67 received the first impulse is also opened while springs 11.8 are closed. Since relay 63 is operated this time the armature 65 is in attracted position and a new circuit is provided for the vertical magnet 67 including the off normal springs 118 and the armature 65 and its make contact. Due to their slow release characteristics, the relays 59 and 63 remain operated during impulsing.

After the last impulse of the series, the relay 63 restores and transfers the impulsing circuit trom the vertical magnet 67 to the r0- tary magnet 100.

Vfhen the calling subscriber operates his calling device for the second digit the line relay 57 will be interrupted again a number of times in accordance with the digit dialled, and at its back contact and armature 58 it will close the circuit for the slow release relay 68 in series with the rotary magvenergizesi which happens shortly a ing of switching relay 92 in order to prevent a ipremature operat onof the switching relay; as the private Wiper 103 passes over idle lines. At its armature 7 O the relay 68sh0rt "circuits the normally closed contacts controlled by armature 74, throughv which the impulse circuit is taken, so that this'circuit will not be opened when the relay operates as the private Wiper 103-passes over busy lines. ,Therotary magnetlOO rotatesthe shaftandjwithit the wiperslOQQ 103,wand

104, advancing them to the contacts otthe desired line. Duetotits sloW-to-release characteristics, the relay 68 remains operated dur-i ing impulsingt i It will be assumed firstthat the line to Whichthe Wipers have been advanced is busy. The private -contact,isuch as 106, of a busy linejsfconnectedto ground. Whenthe pri vate wiper 103 encounters the busy contact acireuit will be closed forthe relay 72 which includes armature 69 and its make contact, interrupter springs 19 1 controlled by themtary magnet, indingjf-relay72 to battery. Relayl .7 2 operatesits armature? 3, connecting therebyground from the holding conductorl60 to the conductor 101 in order to insure its Qoperation after the relay 68 detransmiss on of impulses ceasesr At its 7 armature Z4a,the;relay 72 opens the-origlnal en ergizing circuitsi'of relay 68; and at its armature 75 "a circuit is closedfor the transmission] of the busy tone. to the calling subscriber,v which circuitincludes the armatures 66, 71 and- 75 and whichlwill be completed upon the ideenergization o-t relay 68: and retraction of armature 7:1. Relay/mat itsy'armature 73 disconnects thelower Wind ng of the switching relay 92in order to prevent an energization of this relay in case the busylinelshou ld become idle;

ceiver' o-peningthereby the circuit for the i a ,line relay 57. The linerelay restores and gy i fi fi When the calling subscriber tone transmitted overthe conductor 66" over a circuit" intimated above," he replaces the reopens the circuit of the slow release Zrelay5 9. Thisrelay removes ground from' the holding conductor 60 whichgcauses the deenergizationflof the relays v "and-relayfiiZ a -A.t

its armature 61 and "tsresting contact the y be circuitjis closed for release magnet 168. from groundvlover armature 581 and its resting contact, spring 611and :its resting contact, offnormalsprings 11 5 and Windmigiof therecase the ecalled line is 1 free from V the after the switchingrelay 92 Will operate over a circuit from ground onthe holding conductor armature 73, and its resting contact, lower Windingor the switching relay92, resting contact and armature 69 private vviper 103, contact106 of thejidle line, and to battery over the cut-off relay such as 15 in seriesvvith the lower indingfot line relay such as 19 of the called line. 'lhesvvitching relay 92,

at its armature connects the grounded hold ing conductor 60" directly to the private Wiper 103for markin the called line busy to othenconnectors. At armature 96, the switching relay connects itself in aholding circuit involving its upper Winding, and the holdlng conductor 60 at armature 981tfd1sconnects the rotary magnet at armature 94 it prepares the ringback circuit; and at armatures 93 a and 99 it closes the ringing circuit which extendsi from grounch restin contact and armature91, armature 99 and its make contactywiper i041, bank' contact 107,' condenser and ringer in series with the switchhook of the'called station, bankicontact 105, Wiper l02, mal;e contact andlarma; ture 93, armature 87 and its resting contact, I

lower Winding of the ring cut off relay 86, to battery at an alternating current source. In the present case rlnging current is superimposedupon battery and connected to the lower vvinding ofrelay86over conductor 86,

A fraction of the generator current :traverses a circuit over the condenser 88 andthe. a telephone at the calling station togive'the calling party the ring-back tone. 5 a

When the receiver-isqremoved at substation,1 the ringer and the condenser ate which are normally bridged across the line a conductors are removed, and a direct loop circuit is-provided overwhichthe ring-cut ofl'. relay 86 qberates. At its armature 89; this relay closes a holding circuit for itself-Lover its upper Winding, to the groundedholding a "conductor 1 60 at its arlnatures 87 and it 9; it svvitchesjthe linethrough and cuts off the ringing; currentwand at its" armatu1'ej90,

the {relay 86 closes at circuit for the lower 3 winding of -the backbridge impedance '76 {for transmitting talking current to theqcalle'd line; This circuitextends: from; ground, make contact and armature 197; armature 90 and; its makefcontact, lower windinglof im-v pedance76, armature 80 and its restingcontact make contact and armature 915armature 99 and its makecontact, wiper 10 i, bank con tact 107, loopot the, called substation, bank "contact,1Q5',; iper,102 make contact and armature 98, armature 87 and its makecQn tact, resting -contactandj armature 79, and: upper vvinding of the impedance '76 to battery. The calling station receives talking current byway of the windings otline relayb'Z. a a

j "The subscribers replace their receivers at l the end ofthe conversation. -When the reo v 1etth r c ll gl sta ons rep ac a the circuit to the line relay 57 is open. 'This relay restores and opens the circuit of relay 59. When relay 59 restores, it removes ground from the holding conductor 60 at its armature 60, thereby opening the holding circuits of relays 50, 86, and 92. At armature 62 the relay 59 removes ground from a contact in the bank of the distributor which is accessible to wiper 34. At its armature 61 it closes the circuit to the release magnet 108 which has been traced previously. The release magnet operates, allows the shaft to return to normal and to restore the 0H normal springs, which open the circuit of the release magnet.

The entire equipment is now in position of rest and ready to serve for the extension of another call.

The operation of the equipment in connection with outgoing service'to the main exchange will be described next. By outgoing service is meant the extension of a call from a private branch exchange station, such as station A, to a distant main exchange. Trunk lines terminating in a distant main exchange are accessible to the connector C over a certain level, in the present case over the ninth level. The switch is arranged to give outgoing service only to those lines whose associated line and cut-off relay circuit does not ground the discriminating trunk 13 which is accessible to wiper 22 of the finder switch. Therefore, lines which shall receive outgoing service will not be provided with a discriminating conductor such as 13. The contacts which are operated by the spring 14 shown at the left of relay 50, will be operated when the shaft of the connector switch is raised to the ninth level, and the contacts which are operated by spring'14 will be operated when the switch shaft is raised to the ninth or to the tenth level. The physical arrangement by which contact springs such as 14 and 14 are actuated is disclosed in the application of Hans Sengebusch, Serial Number 54,597, filed September 5, 1925.

When a subscriber operates the connector C to the ninth level, provided he is entitled to outgoing service, the connector will rotate automatically and hunt for an'idle trunk line terminating in a distant exchange. However, when a. subscriberwho is not entitled to outgoing service actuates the connector to the ninth level, the connector will rotate its wiper past the last available trunk, due to the discriminating conductor 13 being grounded, and the subscriber will receive a busy tone. v r

The operations intimated above, will now be explained in detail.

When the subscriber at the calling station operates his calling device, the line relay 57 will deenergize in accordance withthe dialled digit, as was described previously, and will transmit impulses to the vertical magnet by way of the series relay 63. The release relay 59 was, of course, operated immediately upon the first energization of line relay 57. The vertical magnet 67 raises the wipers of the connector opposite the ninth level. When the ninth level is reached, both sections of the normal post springs 14 and 14 operate and connect the discriminating trunk 13 through to the private wiper 103 by way of the armature 52 of relay 50, contact spring 110, and wiper 22 of the finder switch.

It shall be assumed first that the calling subscriber is not entitled to outgoing service.

Accordingly, the connector must rotate in the ninth level without engaging with any of the outgoing trunks leading to the distant main exchange, and busy tone must be transmitted to the calling subscriber. This is done as follows:

Since it is assumed that the calling subscriber is not entitledto outgoing service, the discriminating trunk 13 is provided, that is, ground is transmittedover the wiper 22 of the finder switch, and over a path which was traced previously, to'the p'rivate wiper 103. Thisground on the wiper 103 actuates the connector as if all trunks encountered in the ninth level were busy, i. e.,' the connector rotates the wipers oif the bank and transmits busy tone to thejcalling line,

Relay 63 restores when the calling subscriber has finished dialling. Relay 72, prior to the deenergization of relay 63 is operated from ground on springs 112, springs 120 and 119 of an off-normal contact which is adapted to operate on the eleventh rotary step of the ninth and tenth level, armature 64 and its make contact, conductor 101, interrupter spring 101, and winding of relay 72 to battery. At armature 74 the relay 72 prepared the circuit for the rotary magnet 100, which is effective upon the deenergization of relay 63, from ground on'springs 112, springs 120 and 119, armature 64 and its resting contact, armature 74 and its make contact, winding of relay 68, restingcontact and armature 98, winding of the rotary magnet 100 to battery. The rotary magnet operates and opens its interrupter springs 101,'thereb-y interrupting the circuit of relay 72. This relay in turn interrupts at its armature 74 the circuit for the rotary magnet 100. WVhen the rotary magnet deenergizes'it closes its interrupter springs 101 thereby again closing the circuit for relay 72 by way of the armature 69 of relay 68 which is slow acting and is therefore in operated position. The ground for the reoperation of relay 72 is in this case derived from the discriminating trunk 13 by way of the wiper 2201 the finder switch, normalpost springs 110 and the armature 52. Upon the operation of 72 it closes the circuit for the rotary magnet again at its armature 74. The rotary magnet accordingly energizes, opening at its interrupter contacts 101 the circuits for relay 72. This interactionbf the rotary magnet andthe relay -72 continues until the wipers-102, 103 and 104' rotate past the eleventh contacts irrthe ninthlevel; At

this time the spring 120 is operated, connect;

ing the groundfrom spring 112 to the conductor-101. the condition in which the Vance to the eleventhrotary step inthe ninth level, Relay 68 releases after awhile, and

closes at its armature 71 the circuit for the transmission of the busy tone from the conductor 66 by way of the armaturesto,

andfi' -fl V i when thesubscriber replaces his receiver in response to recognizing the busy tone, the

ies graph."

the following-manner? i i. e f ,Relay 63 is operated during theflvert'zcal operation of the switch "and has its armature switch is released in a manner which has already been described in a previouspara- Iti will next be assumed that the subscriberwho operates the connector to the ninth level is entitled to outgoingservice. In this case'the wiper'22 of the finderswitch does notf transinit ground to the private wiper 103 as in the previous case since the discriminating conductor 13 1s rnisslng. The connecuntil it encounters an idle trunk leading to a main exchange. his s acooinphshedun "64 in operated position. Therefore, when thenin-th level is reached, ground is mitted for the operationof relay *Tirom the spring 112 or the nornialhpost contact, by way otsprings 120 211161 119, armature 6 1 anditsmake contact, conductor 101' interrupter contactlOl, winding 72, to battery, Relay TQagain attracts armature .7 1, thereby preparing a circuit; for the operation of the rotaryinagnetf100. which will be effective exactlyas in theprevious caseun on then-clerenergizationi of relay 63, shortly after, the

impulse. transmission for] the vertical magnetG'T termmates; Therotary magnet receivesstherefore,an irnpulse immediately iipon ;the restoration 'otrelav 63 and opens the clrouit of the. rolay'72 hilt S spring 101. The wipers of the connector are now inen- ,gagernent V with the first trunk leading to connector must :take another rotary step and advance the wiper into engagement with the UG) 2 M the main exchange, If ;this trunlrf idle, the connector must stop andficonipiete the connection from calling" subscriber tothe idle trunk. If the trunk is busy, h'oi vever',atlie n xt trunk. 1 e r and which-close when the, wipers ad- It shallbe :assumed that the first trunk encountered by the connectorfis busy. If

this isthe case, theprivate Wiper 103 finds ground. taken its step, its oirouitris opened at armathe relay 72, which: may be tracedffrom ground encountered by wiper 103, jarmature 69 and its make contact, conductor 101, in terrupter'spring-101, and winding ofrelay 72 to battery. Belay 72 therefore energizesand closes atits armature lithe previously traced circuit for .the rotary magnet 100 i inagnettakes another step, advancing its wipers totheynext set ofbank ContactsassO- ciated'with anothentrunk line. "Upon'en -ergizing, the rotary magnet opensitsinterrupter springs 101, there'by opening the cirwhich involves the relay 68. The rotary cuiuforrelay 72, and this relay, in deenergizing, opens at the armature 1 the c1rcult for the rotary magnet 100. i

Shortly after the rotary magnet 100 has However, being i I 1 176 ture 7 1 of relay 72 which in turn-was interi no lncase the second trunkis foun'd busy, re i lay 72 will again operate, and willcl ose the circuit for the rotarymagnet, which will take 1 another step in precisely thesame manner as i was already described, tor willtherefore rotate 'in theuninth level hen an idle trunk is encountered by the wiper 103 no ground will-be, found, and, ac -1 'xcordingly, a reenergimjtion of the relay '72 is impossible. The rotary magnet 100 :will

therefore not take ano'ther step and will keep the, wipers 102 to 10 1, inclusive, in engageinent' with the idle trunlc line. The switching relay 92 willbe operated from ground on the holding conductor GOQ'armaLure 73 and its resting contact, lower; winding of. the

switching relay92, resting contactand armabattery over a-relay at the main exchange.- At its armature 96, therelay 92 provides a locking circuit" rgrwitself: involving its! upperfwindi'ng to= groundat the holding conductor 60"; at armature 98,,the circuit for 'the rotarymagnet is opened, at armature 95, *theprivate wiper 103 is groundeddirectly over the holdingconductor 60 ini order to make the trunk busy to other lhuntingcone nectors; and, dueto the attraction of armae, tur'e 95, *the Wind ng-0t relay '17 isCOnnected inserieswith the lower'winding orthe relay 86 bywayofthe springlllbf the normal post springl l. The winding of relay 'ZZ is connected tothe holding conductor 60" and 'encouiitersbattery over theconjductor 86, in serieswith the lower winding of relay 1 86; Upon operating, relay 77 aamersarmatures 79 and 80, thereby removing the impedance 76 from across the trunk conductors. At its armature 78 and 81 the relay 77 removes the line relay 57 from the line circuits. Relay 86 also operates in circuit with relay 77 and locks itself over its upper winding and its aramature 89 to the holding conductor The connection extends now directly to the trunk conductors and may be traced as follows:

Wiper 102 which is in engagement with a bank contact associated with a trunk conductor, make contact and armature 93, winding of relay 84, make contact and armature 78, armature 51- and its make contact, wiper 21 of the finder switch, line conductor 7, loop of the calling line, line conductor 8, wiper 24 of the finder switch, make contact and armature 56, armature 81 and its make contact, make contact and armature 91, armature 99 and its make contact, wiper 104 which is in engagement with a bank contact associated with the other trunk conductor.

Therefore, the loop of the calling substation extends in a clear metallic circuit to the mainexchange over the trunk seized by the connector. Relay 84 is energized in the circuit and has operated its armature 85 which provides a holding circuit for the release relay 59. This is necessary since the release relay must remain operated, and since its original circuit has been opened at armature 58 of the deenergized line relay 57. Due to a slow release characteristic, relay 59 remains operated in the interval between the restoration of relay 57 and the operation of relay 54C.

The succeeding series of impulses from the calling substation cause the switches in the central office to complete the desired connection in the usual manner.

The release of the connection takes place when the calling subscriber replaces his receiver. The circuit for relay 84 is thereby opened, and this relay deenergizes retracting its armature 85, which interrupts the circuit for the slow release relay 59. Relay 59 releases, and, upon retracting its armature 60 it opens the holding circuit for relays 50,77, 86, and 92; at armature 62 it removes ground from a bank contact of the finder distributor in order to mark the finder switch F idle; at armature 61 the circuit is closed for the release magnet 108 from ground, armature 58 restoring, closes the circuit to relay 72 over the cam springs 121 and 120. Relay72 at its armature 74 connects the rotary magnet again to the circuit, which, however, is incomplete on account of the cam springs 120 and 119 being separated. A further rotation is therefore inhibited. At its armature 75, the relay 72 closes the circuit for transmitting to the calling party the busy tone. This operation, as well as the operations for releasing the switch when the subscriber replaces his receiver in response'to the busy tone have been described in detail previously.

The tenth level of the connector is reserved for extending calls to the attendant in the private branch exchange, that is, the connector has access over the tenth level to trunks terminating in the attendants cabinet. The operations of the equipment in connection with service to the attendant do not materially differ from the operations already explained. The service will therefore be described only briefly and circuits will be traced only where it is necessary for the sake of easy understanding.

lVhen the calling party operates the calling device in accordance with the digit designating the tenth level, the line relay 57 will follow the impulses, and, at the back contact of armature 58, will close the circuit to relay 63 in series with the vertical magnet 67. The vertical magnet raises the shaft, moving the wipers to the tenth level.

The normal post spring designated 14: operates on the ninth step of the shaft and closes the circuit to relay 72 through the make contact and armature 64: of relay 63.

Accordingly, relay 72 operates.

At the termination of the impulse series, relay 63 restores and closes the circuits to relay 68 and the rotary magnet 100. The rotary magnet rotates. the shaft, advancing the wipers to the first trunk, and opens the circuit to relay 72. This relay restores and opens the circuits to relay 68 and to the rotary magnet.

In case the first trunk encountered is idle, the connector switch seizes the trunk as explained previously in connection with the service to the distant main exchange.

In case the first trunk should be busy, the rotary magnet on restoring, closes the circuit to relay 72 from ground on the private wiper 103. Relay 72 operates; closes its locking circuit; and closes the circuit to relay 68 and to the rotary magnet. ,The rotary magnet, accordingly, rotates the shaft, advancing the wiper to the next trunk and opens the circuit to relay72, which restores and opens the circuit to the rotary magnet. The foregoing operations continue until an idle trunk is found or until the wipers pass off the bank in the tenth level.

When an idle trunk is found, removal of relay 59.]f Upon restoring, relay 59 removes huntingflforan idle trunkleadin'g tofa jdistant main eXchange.

ground from the private wiper 103 prevents further closing of'the circuit tolelay 72. Relay" 68 restores and closes the circuit to the lowervvinding of re1ay92 in series with a relay in the attendantcabinet. The switch ing relay'92operates closes the circuit to its locking Winding; opens a part of the incomplete circuit to relay 68 and to the rotary Inagnet 100, leplacestbe indirect ground on the private wiper with direct ground; and

* connects generator current to the calling line through the condenser 88 tofgive the calling described.

party the ring baclrto'ne. h i y When-the attendantanswersQa loop cir cuit is provided for'th e' operation oflrelay 86 over its lower winding. Upon operating relay 86 closes the circuit to its upper locking windingat its armature 89; remg )ve s'the ring back tone from thecalling', line and connects ance 761 battery to the trunk through theimped-j The attendant in the'private branch ex; change completestheydesired connection, and

conversation can take place. talking current being supplied "to i the calling station over the windings of relay 57.

on thetermination"ofthe call, the calling subscriber replaces his receiver and opens therebythe circuits to theline relay 57. The linerelayres'tores and opens the circuitto the ground from the distributor banlecontact accessible to Wiper 34 opens the locking vcircuit torelays 92, "86, and andcloses thiecircnit to the releaselinagnet 1 08, to cause th'econnector to release inagmanner already In case all trunksaccessible to the tenth level of, the connector should be busy, the

shaft, on the eleventh rotary step, operates the cam springslQQb Therotary magnet on restoring, closes the circuit to relay 72 from ground through the camspring121 and120, The operation of the switch, from this point on is ashexplained in connection withthe i p The operationof the eduiprnent in the at \tendantls cabinet will now be explained with reference a to Figs. ,2 and 3. However, be

foreopening the discussionofthe equipmentfshowjn in these figures, adiew outstandingfeatures-willbe recalled which havebeen mentioned briefly, inanother paragraph,

Fig. 2 shows trunk line comprising the triink'conductors 200, 201, which trunk line connects theprivatebranch exchange with a main exchange, and terminates in the private branch exchange in the attendantscabinet as shown in Fig. 2. h Connections are branched oil from the trunk line to equipment in the attendants cabinet in orderto provide means for certain; operations involving the attendaht,and the trunk l ne, as shown in th s figure terminates normally in an incon ing iconnector switch shown in Fig. 3. h y p The outstadingfeatureinconnection with the attendants cabinet consists in the unifi-fcation and combination of various relays which are common to a plurality of trunk lines. These relays are'shown in the lower part OfFigQ. The trunk line200-2Ql is zttwo-waytrunk line and-is, accordingly, faccessible to local connectorsiin the privateibranch exchange over the conductors 202, 203, and 20% which terminate in bank contacts inicertain levels of the connectors "such asthe, one shown in vided for night service. Theseiconductors terminate inthe line equipment ofa prede-f termined substation, and, by throwingfthe key 208, the attendant connects-the incoming trunkfrom the main exchange direcjtlydto this substation. A call, coming in fromthe the key 208, always terminate at this substation.

extending a call from the private branch ex change by way of selectorsto a desired party in the mainexchange. Normally, there is ground and battery potential onpthe trunlr' conductors QOO and 201 from the equipment of the lineswitch at the distantend ofthe trunk line. However, should the trunk be seized in the main exchange by a subscriber desiringto extenda connectlon to-the private branch exchangenthe battery and ground p0- inain exchange, will, in operated position'of l I a The trunk, atlts'dlstant end lnthelnain exchange is provided With a lineswitchfor,

tential on the trunk conductors 2001 and 201 will be reversed for a explained later on. i

Various keys are provided at theatten'd ants position, the purposeof whichiwill be described as the" description progresses.

There is also shown anoperators telephone impulsesto'switchesin the privatebranch exchange in ordertoextend a connection to a desired party. I-lowever, ifthe attendant.

purpose whichjwill be desiresto extenda connection over the trunk line to the main exchange, her calling device- 246 will be connected in adirect loop circuit across the trunk conductors 200'and 201 in a manner that will-beexplained subsequently.

In. addition to the equipment intimated above, trunk lines, such as the trunk lines 250 and 266, terminate at the attendants position in keys 248 and 264. These trunk lines are W a so Theconductors 205,266 and 207m proprovided for two-way service within the private branch exchange, that is, a private branch exchange subscriber can reach the attendant by way of one of these trunk lines, and the attendant, in turn, can extend a connection to a private branch exchange subscriber over one of the trunk lines.

Referring particularly to the incoming connector shown in F ig. 3, the principal feature shown in connection with this connector consists in relays which are individual to an incoming trunk line from the main exchange, and in combining these relays with the equipment of an incoming connector.

Of this individual equipment, only the polarized relay 327 will be mentioned at this point of the explanation. This relay is normally bridged across the trunk line extendin to the main exchange, and, since battery and ground potentials are provided on thedistant end of the trunk line, the polarized relay 327 is energized. Accordingly, the polarized relay 327 is shown in operated position, where as the rest of the equipment of the incoming connector shown in Fig. 3 is shown in normal position. 1

The detailed explanation of the various types of service provided at the attendants cabinet will now be presented.

It will be assumed first that a subscriber in the main exchange desiresto extend a call to the attendants position at the private branch exchange. r V

A connector switch in the main exchange seizes the trunk 200 and 201 leading to the attendants cabinet, and reverses the battery on the trunk, thereby causing the polarized relay 327 in the incoming connector associated with the trunk to restore. The polarized relay operates armature 328, thereby disconnecting the conductor 302 from the conductor 303 and connecting the conductor 302 to ground over armature 320 and its resting contact. Following the conductor 302 to Fig. 2, it will be seen that a circuit is closed for the busy lamp 302 and that ground is also extended to the conductor 204 which is the private normal conductor of the central oiiice trunk accessible to a local connector in the private branch exchange. By grounding the conductor 204 in the local connector, a seizure of the central office trunk by a private branch exchange subscriber is prevented.

The connector in the central exchange places generator current on the trunk conductor 200 and 201 in order to signal the attendant at the private branch exchange. The signalling current traverses the lower winding of relay 324 in the incoming connector over the following circuit: Conductor 200, springs 213 and 214 of key .208, conductor 305, resting contact controlled by armature 314, condenser 362, lower winding of relay 324, which is in parallel with an impedance 380, resting contact and armature 322, resting contact controlled by armature 316, coiiductor306, springs 215 and 216 of key 208, and back to the central main exchange over conductor 201. The relay operates and closes at its armature 326 a holding circuit for itself over its upper winding to ground by way of armature 321 and its resting contact. At armature 325, the relay 324 grounds the conductor 301, thereby connecting a circuit for the answering lamp 301 at the attendants position.

The attendant, noticing the glowing of the lamp 301, operates the key 223 in order to answer the call. This operation of the key 223 connects the operators telephone circuit 245 across the central olfice trunk way of springs 228 and 229, and the springs 230 and 231. At springs232 and 233 of the key 223, the impulsing circuit is prepared for the operation of the incoming connector over the impulse conductor 307; at spring 233 and 234, a circuit is closed for the relay 287 which extends from battery, winding of relay 287, resting contact and armature 284, closed impulse contacts of the calling device. 246, re lease key springs 234, spring 233, to ground over armature 285 and its resting contact. Relay 287 operates and closes its armature 288, thereby completing a circuit for the slow acting relay,289. The latter relay operates armature 290 closing thereby another point in the impulsing circuitto the incoming connector. v H 1 At springs 224 and 225 of key 223, a circuit is closed over conductor 303 for the relay 318 in the incoming connector. This relay operates, and at its armature 322, removes the polarized relay 327 and the relay 324 from the trunk conductors, and connects the relay 329 across the trunkconductors by way oi armature 332 of relay 331. This bridging of the relay 329 across the trunk conductors 200 and 201 provides a loop circuit for the operation of the usual ring-cut-ofi' relay in the central office connector, which operates and removes the generator current from the trunk conductors. At armature 321, the relay 318 opens the locking circuit for the relay 324, allowing the relay 324 to restore, and to remove 'at its armature 325 ground from the conductor 301, which extinguishes the lamp 301. At its armature 319, the conductors 302 and 303 are united, and ground is therefore maintained on conductor 302 from the springs 224 and 225 and the conductor 303 in Fig. 2.

Relay 329 operates from current supplied by the connector in the central main exchange, and closes, at its armature 328' a circuit by way of conductor 300 for the operation of the supervisory lamp 300.

The holding key 220 is now operated, which closes a guarding circuit to relay 318 over conductor 303 so that relay 318 will remain operated when the key 223 at the attendants position is restored.

a relay343 connectsjthe relay 347 to the private The attendant obtains the name or number of the party desired in theprivate'branch ex} change and proceeds to set up a connection to 'nector shown in Fig.

that artys line through the incoming con- :Relay 287 of the common relay equipment in]theattendant"s cabinet,is,;-as will'ybe re- 'inembered," in a series circuit" with the impu'lsef cont'acts of the calling device 246. Accerdingly, when the callingdevice is operated, the re lay 2871iollows the impulses of measures from the calling device, and, at

' eaeh deenergization grounds the impulse conduct'or: 307 as follcwsi jGi'ound at armature 288Land its break contact, make contact and armature 290,1spr-ings 233 and 232,*co1'iductor; 307, springs 335 and 334 fo fythe ofi normal contact, winding of the "series relay 340, and winding of the verticalilnagnet 342 toibattery. Vhen the connector stpeth j Sha r t w ly by 0118 S p, h

a name sprin jg a i operated,"openingthe imr lls n r ui b f springs a d and substitutln'g therefor the circuit lneluclingithe spring Relay 340 which is'a slow lacting; relay 'is' energized and has" operated 1 its armature 341. The remaining impulses of the series are therefore transmitted over the spring 3360f theofii-norinalcontact and over "armature, 341 and its make contact. Relay 1289 in the common relay equipment in the attendants cabinet remains operated through- V 'outth'transmission ofiinpulses on account of being. a slow acting relay."

Relay 340; deenergizes i after I: the

terlninationof the impulses'eries and trans-- the im'plulsing.circuit tojthefrotary magnet,358l. Thefrotary magnet operated .by

i the secondseries of impulses transmitted from the attendants calling device 246, in, series W th-th Wiefl s ofu 'elar3 3 a e u' 3 and ,its resting contact, armature 3491and its i'breal; contact; and winding of; the rotary magnet tobattery; Relay 343- energizes in series withjthe rotary' magnet and operates Qarinature345 short circuiting thereby the farm ture'349 norder to prevent a premature.

lopenijngioftheirnpulsing circuit when the reenergizes asthepmyatewiper 360 adyancee'over busy lines. At armature 344,.the

wipereftheincoming connector; u i It willbeassurned-first that the desired line is -lfthis is the case, the private wiper i1360fencounters] ground at the private bank fcentactpf the calledlinaand relay 347 operates. At armature 348, it prepares a locking Tc ircuitfor itself which will be completed by the deenergized relay 343 shortly after the termination of the impulse transmission. At

armature 349, the relajy 347 opensthe circuit the rotary magnet, which, at the deenergization ofrelay 343 will alsobeopened at ar1nature345. Atarmature 350, the relay 347 closes a circuit for the transmission of a busy tone tothe trunk conductor 306. The

' busytone is transmitted over a conductor 351 which terminates in a tone machine. Thus the attendant isinformed thatthedesired line is busy, and will inform the waiting main exchange subscriber.

Assuming now that the desired line is idle,

the private wiper 360 does Inot'encounter ground. Accordingly,the relay 347does not energize. Shortly afterthe terininationeol the imp ulseitransinission, 'relay 343- fdeene gizes and moves'itsarmature 344 into the position shown. This operation connects; the

lower winding of the switchingrelay 352 to theprivatewiper 360, and .completes the circuit for theoperati on of the switching relay 352, from ground on conductor" 302, armature 348 and its resting contact, lower winding ofthe switching relay 352, resting A e e n I n '86 andfbat tery over a bridge cut-ofi relay of 1 contact and armature 344, private wiper 360,

the desired subscribersline equipment. The

"at y switching relay operates and closes alocking circuit over its upper fwinding at itsarma' ture355. At armature 354, direct ground froinconductor 302 is connectedto the private wiper 360 in order to busy theline. At armature 356, the circuit forthe rotary mag;-

net358 is opened; and at arniatures 353 and ing the conductors 309 'and "311, it will be seen, that these conductors are now connected across the incomingtrunk conductors 200 and 201 at ar1natures316 and 314and their make contacts, relay 312 being inoper- Y ated position. Therefore, the calling section of the trunk'line is separatedin, the con- I hector fromthecalled section, .an(l the call. 1s held over the impedance 286. Relay 312 in armatures 315and 317, and has therebyconnectedtheconductors 308 and 310 to the sectuted a ground circuit on conductor 300 for the circuit which was provided by armature 328 of relay 329. n n Since the relay 295 in the common relay equipment operates'in serieswith the relay 312 in the incoming connector when the attendant throws the ringing key 235','it will be apparent that ringing current is transmitted to the called substation over the foli the incomlng connector has alsooperated its Ition ofthe connectionwhich leads to the .2 i called party in the privatebranch exchange;

, a e Atarrnature 313, the relay 312 has substilowing circuits Current source 293, armature 295 and its make contact, conductor 308, armature 317 and its make contact. armature 322 and its make contact, armature 357 and its make contact, wiper 361, bell at the called substation, wiper 35.) ofthe incoming connector, make contact and armature 353, armature 315 and its make contact, conductor 310, make contact and armature 297 to ground.

' The key 235 is not held in the ringing position but thrown at intervals to ring the called station. V

\Vhen the called party in the private branch exchange answers the call, relays 312 and 295 being in position of rest, the circuits for relay 331 in the incoming connector is closed from battery at the central oilice trunk line through the loop at -he called station. Relay 331 operates and opens the circuit to relay 329 at its armature 332. Accordingly, armature 328 of relay 329 removes ground from the conductor 300 and the supervisory lamp300 is extinguished, indicating to the attendant that the call has been answered.

The connection between the calling main exchange party and the private branchexchange subscriber is now completed' The branch exchange subscriber receives talking battery over the trunk line from the central main exchange.

The called party at the private branch exchange restores the receiver to the switch hook when the conversation is completed, and opens thereby the locking circuit including the relay 331 in the incoming connector. Accordingly, relay 331 deenergizes, closing the circuit to relay 329. Relay 329 operates over the loop provided by the interoftice trunk and, at armature 328 grounds the conductor 300 to light the supervisory lamp 300. This serves as disconnect supervision for the attendant. v

The attendant releases the holding key 220. Ground being removed from conductors 303 and 302, the busy lamp 302 at the attendants position will be extinguished; ground is also removed from the private normal conductor 204 terminating in a bank contact of a local connector switch. The interotlice trunk is therefore available for service from the private branch exchange tothe main exchange. Relay 318 in the incomin connector releases and closes at its armature 321 a circuit for the release magnet'339 from ground, resting contact and armature 321. oil-normal springs 338 and 337, winding or" the release magnet 339 to battery. [it armature 322 the relay 318 reconnccts the relay 324 and the polarized relay 327 across the trunk conductors. The

polarized relay operates because the battery of the central ofice trunk is now supplied throu h the line-switch at the distant end in z-i the central main exchange. The non-inductive resistance 380 in parallel wlth the lower winding of relay 324 prevents discharge current from operating relay 324when connected to the trunk. V v

The operat-ionsdescribed in the foregoing in connection with release take placerif the main exchange party has also retired from the connection, that is, if the connector in the central exchange has released the interofiice trunk. In this case battery and ground potentials are supplied to the trunk conductors from the lineswitch at the distant exchange end of the trunk line. Should the calling party the main exchange be still on the line, the connector keeps battery and ground reversed on the trunkconductor, and, upon the release of the equipment as described, the polarized relay in the incoming connector, will remain at normal to hold'the central oflice trunk busy to the attendant and to hold the incomingcohnector operated until the calling party disconnects. .VVhen the calling party replaces the receiver the connector will disconnect from the interoflice trunk and the battery supply of the trunk conductors will be reversed causing the polarized relaycin the incoming connector to operate and to make the central ofiice trunk available for outgoing. service as described.

, The local connectors, suchas the one shown in Fig. 1, have access to the central ofiice trunk over the outgoing level. When a connector in theprivatebranch exchange seizes the central office trunk it grounds the conductor 204 causing the lamp 302' toglow, and closing the circuit to relay 318 in the incoming connector. Relay 318 operates, locks to ground on conductor 302, and removes the relay 324 and the polarized relay 327 from the trunk, clearing the trunk of attachments. I i

The local connectors in the private branch exchange have also access to the attendants cabinet over trunks designated 250 and 266 shown in Fig. 2. 'When a calling subscriber in the private branch exchange operates a connector such as the one shown in Fig. 1, into connection with one of these trunks, say with trunk designated 250, the conductor 253 will be grounded, and a circuit will thereby be completed by way of the springs 255 and 254 to lamp 249. This serves as a signal for the attendant notifying her that a call has been extended by a private branch exchange subscriber. The attendant operates the associated trunk key, in the assumed case the key 248, thereby connecting her telephone circuit 245 across the trunk 250. This circuit may be traced from conductor 251, springs 272 and 273 of key 248, release key 247 and impulse springs of the calling device 246 in series, springs 261 and 260 of key 248, switchhook, receiver and transmitter in series, springs 257 and 256, and conductor 252 to the calling branch exchange subscriber.

herof t-heparty desired, and restores the .1 V i closed for the operation 'ofthe relay 283m trunlrlkey 28 ,Shethenproceeds to set up the ,connectionto the desired party over a central office trunk; The private branch ere ,changesubscriber requesting the call disconfiC f nd aits until heiscalled by the at tendant. v it 1 The a operates the key ated,,v. 'iththe; central othce trunk, thereby connectinghcr telephone circuit across the trunlr conductors and closingthe circuits to relay 318 in the connector in, a manner already described. Relay3l8 in the incoming connector operates and causes the busy lamp armature 319. Ground, itwill be rememberedjis. at this time also on conductor 204 which marks the central othce trunk busy to other calling connectors in the private branch exchange. Relays 324 and 327 are removed froin across the trunk conductors, andthe loopc rcuit to the mam exchange ,1s closed byww aytof relay 329 inthe incoming, connector The attendant next operates the key 336, transferring thereby the loop circuit across the central oflice trunk from relay 329 1 .1 the incoming connector toher dialling the common relay equipment at the: attendantspositionin series with th'e'relay 312 in the incoming connector which maybe traced from ground, Winding of relay 283, sprmgs 23 8fja nd 237,;springs 227 and 226, conductor ,304, inding of relay 312 to battery.

n The operation of the two relays 2 83 and 312 responsive to the actuation oflrey 336 effects the transfer of the loop circuit of the intero'fiice trunk trom relay 329 to the dialling equipmentjof the operatorvvhich may be traced-as: followsz1 Conductor 200, springs 213and 214i, conductor 5, make contact and armature 314.,conductor 311, make contact and armature 285,, springs 233 and 2341, re-

lease key 247, impulse springs 2 16, armature 284;} and its make contact, conductor 309, ar-

mature 316,:and its make contact,'conductor 306,"1'springs 215 and 216, and trunkconductor 201 back tofthe' central exchange.

The operator the private branch can change now, dials thenumb'er of the party desired, actuating thereby the switches in the central ofiice to set up connection to the line ,ofthe anted party. The key336 is restored after the required digits have beentransmih tedto theflcentral office; switches, and, upon restoring the key, the operators telephone circuit is'again connected across the central ofiice trunk, and the trunk loop, Which, during "dialling entendedover the calling device 24i6is againtransi'erred to the loop including relay329ot' the incoming connector. Relay 329 ithereiiforeoperates and connects ground to ing the impulsedevice 246 at the attendants position was brought about by the restoraground at its armature 285by ay of springs conductor 300 lamp 300', i i y The reconnection of the loop including the relay 329 in substitution of theloop includ in ordertolight the supervisory us and 234, and over the impulse device 246,

in orderto prepare the impulsin g circuits for a the incoming connector shown in ig'. 3. y H p If the desired party in the mainexchange' 302; to glow by grouncling conductor3O2 at 7 answers, the attendant; at theprivate branch exchange will proceed to set up the connection to the private branch exchange subscriber W110 requested the call. This connec- The incoming connector isthus operated into connection with the line of the private branch exchange. subscriber ivho'requested the call.

The key220 at the ,attendan ts position is next operated in order to hold the connection, and the key 235 is operated in order to transniit ringing current tothe private branch exchange subscriber. The ringing operation which follows the actuation of the ringing key 235 has alreadybeen described in detail and shall not be repeated. WVhile ringing current is placed on the line, the connection to the party in the central ofiice is held through the impedance 286 at the attendants position in the usual manner. 1 H I WVhen the'private branch exchange subcircuitover the central oflice trunk, which circuit includes the relay 331. This relay op crates and opens at its armature 332 the circuit of the relay 329. 1 Relay 329 relea'sesand opens the circuits to the supervisory lamp 300 which indicates to the attendant that the branch exchange subscriberhas answered. The connection is now held by the subscriber Whorequestedthe call byway of both trunk onductors and the relay 331 in the incoming connector. i a

Relay 331, in the incoming connector restores When the party who requested the call replaces his receiver, and,in restoring, Icon nects the relay 329 across the central office trunk to naintain aloop for holding the con nection inthecentral oifice. Relay opscriber answers the call he completes the loop '1 erates and causes the supervisory lamp 300 to glow in order to notify the attendant that the private branch exchange party has retired from the call.

The attendant then releases the connec-' tion by operating the holding key 220 into normal position. This removes ground from the conductor 303 and from the conductor 302. The busy lamp 302 is thereby extinguished; ground is removed from the private normal conductor 204 terminating in the multiple of the local connector switches; making the central oiiice trunk available for outgoing service; and opens the circuit of relay 318 in the incoming connector. Relay 318 restores and removes relay 329 from across the central oliice trunk causing the connection in the cen* tral office to release.

The attendant, as was previously intimated. has access to the local connectors over the trunks such as 250 and'266 terminating in keys 248 and 264 respectively. When the attendant desires to establish connection with a private branch exchange subscriber, she operates a trunk key such as 248 for ex ample, connecting her telephone circuit 245 across the trunk conductors 251 and 252, which causes a finder switch, such as the one shown at F in Fig. 1, to find this trunk 250 and to extend it to a local connector such as the one shown at C in Fig. 1. The attendant dials the number of the party desired, causing the local connector to set up a connection. The dialling circuit extends in this case from the trunk conductor 251, springs 272 and 273, release key 247, impulse contacts of the calling device 246, springs 261 and 260, switchhook of the operators telephone circuit 245, contact 245, which is operated by the dial 246, springs 257 and 256, and back to the local connector over the trunk conductor 2 2.

Should the trunk 266 be taken in service instead of trunk 250, the dialling circuits may be traced from conductor 268, springs 272 and 273, springs 258 and 257, contacts 245, switchhook of the operators telephone circuit, springs 260 and 259, springs 276 and 277, impulse springs 246, release key 247, springs 2'79 and 278, back to the local connector over the trunk conductor 267.

It will be apparent from the above explanation that the dialling circuit employed by the attendant at the private branch exchange differs with the service rendered. \Vhen a call is extended to a private branch exchange subscriber by taking into use one of the trunks 250 or 266, the dialling circuit involves a loop circuit with the impulse contacts of the calling device 246 directly bridged across the dialling conductors. The same is the case when the attendant at the private branch exchange desires to extend a connection to a subscriber in the central main exchange. However, when the operator at the branch exchange extends a call to a branch exchange subscriber by way of the incoming connector shown in Fig. 3, which is the case when a central main exchange subscriber calls the attendant and requests the connection to a branch exchange subscriber, the dialling circuit will involve the interrupter relays 287 and 289 which are controlled by the attendant by means of the calling device 246.

The conductors 205, 206 and 207 are, as has already been intimated, reserved for providing night service. When the night key 208 is in operated position, the night telephone connected to the conductors 205, 206 and 207 is directly connected with the central otfice trunk. The central office trunk is made busy to other connectors in the private branch exchange at springs 209 and 210 of the key 208 which connects ground to the private normal conductor 204 terminating in bank contacts at local connectors. The number of night telephones required govern the number of central ofiice trunks used for night service.

The purpose of the release key 247 will be explained next. It will be remembered that the release key 247 is, in every case Where the calling device 246 is used, connected in series with the impulse contacts. Should the attendant desire to release a partly established connection, she will stop operating the calling device 246 and will open the release key 247. This of course opens the loop circuit to the switch in question and that switch releases. This provision is necessary since it may happen that the operator discovers during the operation of the impulse device 246 that she has dialled the Wrong number. In order to forestall wrong connections she has melzlms in the key 247 to release an incompleted ca At 280 is shown a buzzer which may be connected to an armature 292 of relay 291 by means of a key 281. This provision is mostly used in night service or under similar conditions, for example, when the attendant is also charged Withvarious other duties auxiliary to her duty of attending to the switchboard. If this is the case, the key 281 is in operated position and at spring 282 the buzzer is connected to the armature 292 of relay 291. Now, should a call come in, regardless whether the call is from'the central exchange or from a subscriber in the private branch exchange, the relay 291 will in any case be operated and will operate its armature 292 thereby closing a circuit for the buzzer 280.

Having described the equipment in detail, it will be seen, that the invention discloses a very efficient and relatively simple arrangement useful for private branch exchanges. It will be understood that modifications are possible without departing from the spirit of the invention, and it will therefore'be appreciated that it is not desired to use the invention precisely as shown in the accompanyingdraivings but. to apply its tea? turesinvaccordancev with the! scope oi the appendedclaims; v u lhatis claimed is: 1 J

I 1; In a telephone syste1n,:a main exchange, a private branch exchange provided with an 7 attendants position, a two, conductor trunk line interconnecting:saidexchanges and; termlnating atxsaid POSltlbIl, calling device, means at said positlon for. connect1ngsa1d calling device directly; across said trunk line for directively extending a call to a substation in said main exchange, an automatic switch in said branch exchange, animpulse repeater, means for connecting said calling device and said repeater to said switch, and means in said switch controlled by said repeater in response to its actuation by said calling device for operating said automatic switch to extend a connection to a substation in said branch exchange.

2. In a telephone system, a main exchange, a private branch exchange provided with an attendants position, a two-conductor trunk line interconnecting said exchanges and terminating at saidposition, a calling device, means at said position for connecting said calling device directly across said trunk line for directively extending a call to a substation in said main exchange, an automatic switch in said branch exchange, an impulse repeater, means for connecting said calling device and said repeater to said switch, means in said switch controlled by said repeater in response to the actuation o fsaid callingdevice for operating said automatic switch to extend a connection to a substation in said branch exchange, and means at said position i for uniting said substations in a conversational circuit.

3. In a telephone system, substations, an operators position, switches accessible to said substations and to said position for extending calls, a calling device at said position, means at said position for seizing one of said switches and for directly connecting said calling device to said seized switchfor directively extending a connection to a substation, other switches accessible only to said position, a repeater, means for connecting'said tion, other switches accessible only to said position, an; impulse producing, dcn ice com prislng a plurahty Of;IGIELYS IHGBJDSfOiPSGlZ- ing one of said other' switches and associat i'ngsaid impulse producing device therewith, and: means, for controlling sa'idswitch by means of said impulse device to extend a coin nection toasubstation. H i 1 5. In a telephone system, substations, an

operators position, switcliesqaccessible to u said substations and to said position for extending calls, a; calling device at said position, means atsaid position for seizing one of said switches and for-directly connecting said calling device to said seized switch for directively extending a connectionto a sub} station, otherswitchesaccessible only to-said position, means-for seizing one ofsaid other switches, a repeater, said second means for connecting said calling idevicegand said re peater to saidseized other switch, and means i in said seized: other switch controlled by said calling device for operating said seized other switchto extendaconnection to asubstation. 6. In a telephone system, a private branch exchange, a distant maine-xchange, a plurality of two-conduct ortrunk lines interconnect-T ingsaid exchanges, each trunk line terminat ing in the branch exchange in anautomatic connector switch,an,attendant operators porepeater responsive to? the actuation of said a,

sition atsaid branch exchangehavingmeans for manipulating said trunk lines, a plural: ity of relaysat said position provided for" the common use of all trunk lines and associated connectors,and a plurality of relays provided in each of said connectors and serV: ing exclusively the trunk line associated therewith. f v I i H 7. In a telephone system, a=private branch exchange, a distant main exchange, a plural ity of two-conductor trunk linesinterconnecting said exchanges, each trunk line terminating in the branch exchange in an automatic connector switch, anattendant opera; tors position at'said branch exchange having means for ,manjipulatingtsaid trunk lines, 'a

plurality of relays atsaid position including impulse repeating relays and a ringingrelay for thecommon use of all trunk lines and associatedconnectors, anda plurality of relays provided inf each of! said connectors and serving exclusively the trunk line connected. therewith.

a 8. Ina telephone system, a privatebranch "exchange, a distant mainfexchange, aftwo-v conductor trunk linefl interconnecting said exchanges and terminating in, said branch-V exchange in an automatic,connector switch,

an attendants position at said branch ex+ change,- a manually operable calling device, means for connecting said callingdevice directly to said trunk line for actuating switches in said main exchange to extend a connection. to a: certain station therea,t, a separate automatically a operable impulse transmitter and means for connecting said transmitter to said connector switch for extending a call to a branch exchange station.

9. In a telephone system, a private branch exchange, a distant main exchange, a twoconductor trunk line interconnecting said exchanges and terminating in said branch exchange inan automatic connector switch, an attendants position at said branch exchange, a manually operable calling device, means for connecting said calling device directly to said trunk line for actuating switches in said main exchange to extend a connection to a certain station thereat, a separate automatically operable impulse transmitter, means for connecting said calling device to said transmitter to control the same, and means for connecting said transmitter to said connector to operate the same to extend a call to a branch exchange station.

10. In a telephone system, a private branch exchange, a distant main exchange, a two-conductor trunk line interconnecting said exchanges and terminating in said branch exchange in an automatic connector switch, an attendants position at said branch exchange, a manually operable calling device, means for connecting said calling device directly to said trunk line for actuating switches in said main exchange to extend a connection to a certain station thereat, a separate automatically operable impulse transmitter, means for connecting said calling device to said transmitter to control the same, means for connecting said transmitter to said connectorto actuate the same to extend a connection to a branch exchange station, and means for unlting said stations in a conversational circuit.

11. In a telephone system, a main ex change, a branch exchange, a plurality of two-way trunks interconnecting said exchanges, each of said trunks terminating in a connector switch in the branch exchange, an operators position at the branch exchange having access to said trunks, a calling device and a repeater at said position, means for bridging said device directly across one of said trunks for extending calls from the branch exchange to the main exchange, and means for bridging said device and said repeater across atrunk for operating the associated connector switch for extending calls from the main exchange to the branch exchange.

12. In a telephone system, a main exchange, a branch exchange, an operators position at the branch exchange, a plurality of two-way trunks interconnecting the exchanges and accessible to said position, each trunk terminating in a connector switch in the branch exchange, a plurality of two-way trunks connecting said position with the branch exchange, a calling device and a re peater at said position, means for bridging ROY FIERO GOULD. 

